Special diets are diets which have been modified in some way to bring about specific healthcare benefits.
Most special diets used to help autistic people are ‘exclusion’ diets. This means you avoid or reduce foodstuffs which may harm you (such as additives in the additive-free diet). Other examples of special diets are the gluten-free, casein-free diet, and the salicylate-free diet.
In some diets you have to exclude some foodstuffs but include others, such as the specific carbohydrate diet. This excludes complex carbohydrates (such as those found in rice and potatoes) and replaces them with simple carbohydrates (such as those found in bananas and squashes).
In practice, many diets share similar characteristics. For example, the Feingold diet is a mixture of the additive-free diet and the salicylate-free diet, while the specific carbohydrate diet incorporates elements of the gluten-free diet.
Some people think that diet is a key component of any intervention designed to help autistic people. Some people also think that modifying the diet and the gastrointestinal system is necessary for the success of other treatments and therefore should come first.
Diets are sometimes combined with other therapies. For example, some people advocate following a particular diet, taking one or more dietary supplements and using detoxification techniques such as chelation.
Eating a healthy balanced diet is recommended for everybody in order to maintain good health. Anyone with a particular condition (in addition to or separate from autism) may be recommended to follow a special diet by a dietitian and this should be followed on an individual basis. For example, dietitians may recommend a gluten or milk exclusion diet for various gut problems. Most special diets provide the same benefits for autistic people as they do to people who are not autistic. They do not appear to provide any additional benefits to autistic people. No evidence at all supports the use of most special diets (such as additive-free diets, the specific-carbohydrate diet, and the yeastfree diet). Determining the benefits of other diets (such as the gluten-free, casein-free diet or the ketogenic diet) for autistic people is not currently possible. We must wait until further research of sufficiently high quality has been completed.
Many potential risks lie in wait when withdrawing normal or regular foods from individuals, but especially young children. Some autistic people are faddy eaters. They already have a less healthy and less varied diet than other people. Restricting what they eat even further may reinforce those rigid eating patterns. It may also increase their social isolation (because they can’t eat the same food as their peers at parties or restaurants). In the long-term special diets could lead to health problems if they are not carefully balanced. For example, according to one review: "The combination of food selectivity and restrictive diets can make it difficult to achieve an adequate diet, consequently resulting in an excessive intake of certain foods and/or deficiencies and malnutrition due to insufficient amounts of other foods. In turn, inadequate intakes may lead to the development of chronic and degenerative conditions that tend to appear in the third or fourth decade of life (cardiovascular disease, high blood pressure, diabetes, dyslipidemia, and osteoporosis, among others) or even earlier, in the case of menstrual disturbances, sleep apnea, and psychosocial disorders." Autistic people or their carers who have concerns about their or their child’s diet should seek advice from a responsible health professional such as their health visitor or GP. This may lead to a referral to a dietitian, in particular one with experience of working with autistic people.
Additive-free diets are exclusion diets which require you to avoid artificial additives such as colourings, flavourings and preservatives. Additive-free diets are based on the idea that some additives contain harmful chemicals which can damage the brain.
Some additive-free diets, such as the Feingold diet, also exclude other substances such as salicylates (a group of substances that are toxic to insects and found in all plants) in the belief that these also cause stress to the digestion.
Various people have made claims about different additive-free diets. For example, the Feingold Association of the United States claims that the Feingold diet can be used to treat people with a wide range of conditions including autism and ADHD
The gluten-free, casein-free diet (GFCF diet) involves avoiding all foodstuffs which contain gluten and casein.
Gluten is a protein found in some cereals such as wheat, rye and barley. Oats contain a similar protein and are usually processed in the same factories, so are often included in this diet. Casein is a protein found in dairy products such as milk, butter, cheese and yoghurt.
There are several overlapping theories as to why gluten and/or casein may be harmful to some individuals. For example, some people believe that improperly digested gluten and/or casein (in the form of harmful peptides) may adversely affect the central nervous system. Other people believe that gluten and/or casein may provoke adverse autoimmune responses in the gastrointestinal (GI) system.
Some people believe that harmful peptides and/or adverse autoimmune responses may create some of the core features of autism, such as difficulties with social communication and social interaction, alongside related problems, such as challenging behaviours. They also believe that by excluding gluten and-or casein from the diet, they can prevent these problems.
The ketogenic diet is a low-carbohydrate diet designed to mimic many of the biochemical changes associated with prolonged starvation.
It is used for the treatment of intractable seizures, that is, seizures which have not responded to normal anticonvulsant medications and therapies.
How the diet is supposed to work is still unclear
Some people think that the ketogenic diet is suitable for people with both autism and epilepsy who have not responded to traditional epilepsy medication.
They think that the ketogenic diet can be used to improve a range of behaviours in autistic children including hyperactivity, social interaction and social communication
The specific carbohydrate diet excludes complex carbohydrates (such as those found in rice and potatoes) and replaces them with simple carbohydrates (such as those found in bananas and squashes).
The diet also uses fermented products, such as homemade yogurt, which is supposed to repopulate the gut with beneficial yeasts and bacteria.
The diet is designed to remove complex carbohydrates which are supposed to feed harmful fungi and bacteria.
The diet is sometimes used to treat people with a variety of gastrointestinal disorders, including irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), ulcerative colitis (UC), Crohn’s disease, and coeliac disease.
Some people think that the specific carbohydrate diet is suitable for anyone who is autistic and who has gastrointestinal problems. They think that the specific carbohydrate diet can restore normal gut functioning in autistic people. They also think that this can lead to a range of improvements such as improvements in behaviour